Published: Thursday, August 21, 2014 at 9:00 a.m.

Last Modified: Thursday, August 21, 2014 at 9:39 a.m.

Serena Williams

Tennis player Serena Williams performs onstage at the Delta Open Mic with Serena Williams event on Wednesday, Aug. 20, 2014 in New York. (Photo by Andy Kropa/Invision/AP)

Andy Kropa /Invision/AP

The top-ranked athlete performed "Diamonds Are a Girl's Best Friend" on Wednesday night at Arena in New York City. She danced and swayed her hips in a mini dress as she sang the song in falsetto and attempted high notes.

Williams told the crowd before she began: "I'm really nervous."

She was joined by fellow tennis player Jack Sock, "Orange Is the New Black" stars Laverne Cox and Uzo Aduba, "Glee" actor Darren Criss and comedian Kathy Griffin at the event for Delta Airlines.

"I do like 80s, 90s rock because it's good for my voice," she said before she performed. "The thing about karaoke is picking a song that works for your voice, that way if you sing like a cat — like I do — you can still sound pretty good."

Williams is seeded No. 1 as she seeks her third straight U.S. Open title. She said winning is "super important," but added that there's "no pressure."